Mechanical Stress Induces Ethylene Production and Epinasty in Poinsettia Cultivars1

Abstract

Abstract Mechanically bent petioles of potted poinsettia plants (Euphorbia pulcherrima Klotzsch ex. Willd., cvs. V-14, Eckespoint C-1 Red, Annette Hegg Diva, Annette Hegg White, and Annette Hegg Hot Pink) produced 3 to 70 times as much ethylene as petioles from unstressed plants. The Annette Hegg cultivars which were most susceptible to leaf epinasty after being sleeved for 24 hours showed the greatest enhancement of ethylene evolution after being mechanically stressed for 24 hours. Exposure to 10 ppm ethylene in air produced the same cultivar dependent pattern of epinasty in 4 hours as was produced by 24 hours of mechanical stress. Spraying with 250 ppm AgNO3, an antagonist of ethylene synthesis and action, reduced the severity of epinasty in ‘Annette Hegg Diva’ plants sleeved for 24 hours. The less susceptible ‘Eckespoint C-1 Red’ and ‘V-14’, produced less stress ethylene and were less susceptible to ethylene-induced epinasty.